Tropospheric ozone, a component of smog (shown here over Los Angeles), is one pollutant that is being targeted to help reduce global warming while we await policies to curb carbon dioxide emissions. (Photograph by photos_mweber/Flickr)

Congressional deadlock and new scientific insights force new direction.

The news on the avoid-dangerous-climate-change front seems to get ever bleaker.

And while much is being made of natural gas serving as a bridge fuel between coal-fired power and some future carbon-free energy system, Nathan Myhrvold of Intellectual Ventures and Ken Caldeira of the Carnegie Institution argue in the journalEnvironmental Research Letters that such a strategy will do little to nothing to reduce global warming in this century. To have any impact in that time period, they write, coal-fired power will need to be replaced by “conservation, wind, solar, nuclear power, and possibly carbon capture and storage.”

Non-CO2 Strategies Getting a Serious Look

So what’s a global-warming mitigator to do? Look for alternatives. And fortunately, it looks like one can at least buy us time.

Despite two important caveats — namely that CO2 is the largest single greenhouse warmer we add to the atmosphere, and there is no long-term global-warming solution that doesn’t involve major cuts in its emissions — the non-CO2 greenhouse warmers are not irrelevant. Collectively, they’re responsible for about 30-40 percent of global warming. Key among them are

methane, which comes from such sources as agriculture, landfills and natural-gas leakage;

black carbon (a k a soot), which comes from using low-tech cookstoves and burning biomass; and

Importantly, their temporal characteristics are very different from CO2’s. CO2 emissions largely come from energy generation; the infrastructure and technologies needed for this energy have decades of useful lifetimes, and so change is difficult and slow unless you’re willing to abandon investments already made. Moreover, because CO2 has a long atmospheric lifetime, slowing CO2 emissions enough to have a substantial effect on its concentration takes time — were CO2 emissions held constant today, its concentration would continue to rise for centuries.

Greenhouse warmers such as methane, black carbon and ozone are quite different. Lowering their emissions would not require huge investments or a retooling of our energy infrastructure; on the contrary, in most cases lowering their emissions would involve making current technologies cleaner and more efficient. Plus, their atmospheric lifetimes are relatively short — about 10 years for methane, weeks to a month for ozone, and about a week for black carbon. Cutting these emissions would reduce their concentrations much more quickly than cutting CO2, and have a more immediate effect on slowing global warming.

Tiny air pollution particles known as black carbon (or soot) form in the air when fuels like coal, wood, and diesel are burned. Because they absorb heat from sunlight, these airborne pollutants add to global warming. This animation shows how soot was dispersed around the Himalayas in 2009. Scientists and policy makers are looking to black carbon, among other targets, to help mitigate global warming as a stopgap measure. (Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)

So how effective would a strategy focused on non-CO2 warmers be? Drew Shindell of NASA’s Goddard Institute for Space Studies and colleagues recently addressed that question in a paper published last month in the journal Science. The authors identified 14 measures (see table below) — seven that reduced methane emissions and seven that addressed black carbon — that collectively could reduce net global warming by 2050 by almost one degree Fahrenheit. Not enough to solve the problem, but enough to buy us time to get our act together on CO2 emissions.

14 Measures Addressing Methane Emissions and Black Carbons

Measure / Gas

Sector

Methane measures

Mitigation of methane from coal mines

Fossil fuels

Recovery of leaked methane from oil and gas production

Reducing gas leakage during pipeline transmission

Landfill gas collection and mitigation of biodegradable waste

Waste management

Including gas recovery at wastewater treatment plants

Control of methane emissions from manure

Agriculture

Intermittent aeration of continuously flooded rice paddies

Black Carbon measures

Filters for diesel vehicles

Transportation

Elimination of highest-emitting vehicles

Introduce clean-burning biomass stoves in developing countries

Residential

Substitution of clean-burning cookstoves using modern fuels (liquid petroleum gas or
biogas) for traditional biomass cook stoves in developing countries

State Department Gets Into the Act

A common refrain in international policy circles is that the United States should take a leadership role on climate change. But with the U.S. political climate currently what it is, that’s a tall order. Rather than tilting at the windmill, the State Department (and by extension the administration) has decided to take a different tack: the recently announced international voluntary program called the Climate and Clean Air Coalition to Reduce Short-Lived Climate Pollutants. Launched by six countries and the United Nations, the initiative targets black carbon, shorter-lived hydrofluorocarbons, and methane to achieve “concrete benefits on climate, health, food and energy resulting from reducing short-lived climate pollutants.” In addition to potentially reducing net global temperatures by almost one degree Fahrenheit by 2050, the 14 measures could avoid the annual loss of more than 30 million tons of crops and millions of premature deaths.*

A few mild barbs have been lobbed at the program. For example the World Wildlife Fund cautions that this should not be allowed to obfuscate the real imperative to cut CO2 emissions, and worries about its tendency to shift the burden from developed nations to developing economies where black-carbon emissions and ozone-producing gases are largest. Eileen Claussen, president of the Center for Climate and Energy Solutions, expressed similar sentiments.

The criticisms notwithstanding, I think the State Department is on to something here. The time for just focusing on CO2 emissions is past — that train left the station years ago.

____________________

Note

*In a related initiative the U.S. Environmental Protection Agency announced a program to address black carbon emissions in the Russian Arctic.

Comments

worst-case scenario

http://www.global-warming-forecasts.com/underestimates.php

February 25, 2012, 2:22 pm

What about black carbon from wildfires? And what about black carbon and soot deposition on ice sheets in polar regions? How will the volume of smoke from climate change wildfires impact the level of “dirty snow” soot accumulation and the consequent rate of snowpack melting, flooding, permafrost melting and methane and other greenhouse gases issuing from melting permafrost?

benny

philippines

February 22, 2012, 11:37 pm

I think all the scientist around the world must look closely under the earth .what will happen if the coolant of the earth ( crude oil) is gone??????

@Phillip Evans

New York

February 22, 2012, 12:50 pm

Nobody denies that water vapor plays a role in the greenhouse effect, but that doesn’t mean that adding other greenhouse gases into the atmosphere won’t further increase global temperature.

Furthermore, adding more greenhouse gases to the atmosphere results in what is called a “positive feedback loop.” A rise in greenhouse gases causes a rise in atmospheric temperature which causes more evaporation, further causing a rise in water vapor in the atmosphere — and therefore an even warmer atmosphere!

Surveys show that virtually all climatologists agree that the planet is warming, and that 97-98% of them agree that human activity is the primary (or sole) cause. I’ve yet to hear or read an argument from the denialists/conspiracy theorist camp that hasn’t already been refuted by unbiased sources.

Phillip Evans

Boston

February 22, 2012, 12:01 pm

Water vapor has a larger greenhouse contribution than any gas mentioned in this article.

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